Butler was educated at Mount Anville Secondary School, followed by University College Dublin, from where she graduated with a BCL degree in 1984 and an LL.M.
[3] Butler frequently appeared in matters involving judicial review and planning and environmental law on behalf of the government, An Bord Pleanála and other public bodies.
[15] She acted as legal adviser to an Oireachtas committee on the content of the Thirty-sixth Amendment of the Constitution of Ireland.
[16] Outside of her practice as a barrister, she was a member of the Employment Appeals Tribunal between 1989 and 1992 and was chairperson of the Mining Board from 1999 to 2002.
[19][20][21][22][23][24] In September 2021, she held in an action taken by Patrick Costello that ratifying the Comprehensive Economic and Trade Agreement would not be contrary to the Irish constitution.